The present invention relates to a power generator, and more particularly a generator which provides power to a rotating field of a propeller.
The hazards of aircraft flight in atmospheric icing conditions are well known. Various techniques are known for removing or preventing ice accumulation encountered during flight. Certain of the techniques are particularly adapted to protect specific parts of an aircraft. An electrothermal propeller de-icing system is an example of a specialized system.
In one electrothermal propeller de-icing system, electrothermal de-icers are bonded to the leading edge portions of each propeller blade. An engine driven alternator is mounted in the stationary field to generate electrical power for the de-icing system. Electrical power from the alternator is conducted to the rotational field of the rotating propeller and hub assembly through a sliding contact typically including a slip ring and brush assembly. Although effective, conducting energy from the stationary field to the rotational field maybe relatively weight and maintenance intensive.
In another propeller de-icing system, a generator is arranged in an annular ring about the rotating propeller shaft and is driven thereby. Disadvantageously, the generator is relatively large and heavy as it is powered by the relatively slow rotation of the propeller shaft.
In addition to providing significant electrical power for the de-icing system, advanced propeller control and actuation requires still more electrical power in the rotational field of the propeller for propeller blade actuation and control. Such significant quantities of electrical power may not be achieved by conventional generators within the limited packaging constraints of an aircraft environment.
Accordingly, it is desirable to provide large quantities of electrical power directly to a rotational field of an aircraft propeller system without complicated, heavy and maintenance intensive rotating couplings.
The permanent magnet alternator (PMA) according to the present invention is located within a propeller shaft. The PMA includes a stator mounted to the propeller shaft such that the stator rotates with the propeller shaft and a rotor which is mounted within the stator and is driven directly by a turbine output shaft. The rotor is thereby driven at the relatively high speed of the turbine output shaft while the stator is driven at a relatively slow speed of the propeller shaft as reduced by an in-line gearbox. The great difference in speed between the propeller shaft and the turbine output shaft results in a relatively compact PMA which provides a significant power output. Moreover, as the propeller shaft and the turbine output shaft preferably rotate in opposite directions, the PMA rotational speed is the sum of the propeller shaft and turbine output shaft further increasing power output.
As the stator of the PMA rotates with the propeller shaft, power is supplied directly to a multiple of propeller blades through a power lead. The power lead rotates with the stator and propeller shaft to provide power directly to the rotating hub and blades. The heretofore necessary slip ring and associated electrical transmission components which transfer power generated within the stationary field of the engine to the rotating field of the propeller are eliminated.
The present invention therefore provides large quantities of electrical power directly to a rotational field of a propeller system without complicated, heavy and maintenance intensive rotational couplings.